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previous: Ethan Effect Of Chokes On Tone? -- 3/13/2000 6:13 AM

Re: Effect Of Chokes On Tone? /Probably too long!

3/13/2000 8:18 AM
Bruce	Re: Effect Of Chokes On Tone? /Probably too long! Well, not taking into consideration the added benifit of less AC ripple from the inductance of a proper supply choke, what I've found to be at least equally important is the DC resistance of the choke and what pure DC resistance would be used (a resistor) in it's place. When the DC resistance of the choke is low like under 100 ohms, then the voltage drop across it at idle and under load is less and ripple rejection is much better then a simple resistor. Remember... I*R=E More voltage is supplied to the screens and the preamp stages through a 90ohm choke then a 500 to 1000 ohm resistor (in the same place). Current flow through either resistance will result in a voltage drop across that resistance, but, lower resistance creates lower voltage drop and higher current flow results in a larger voltage drop. If the power tube's screens draw Xma of current under idle conditions and Xma x 2or3 when the amp is cranked up, that little 90ohms is not going to be dropping as much voltage as a 500 to 1000 ohm resistor. Since the screen's voltage drops more with the larger screen resistor then a choke, the power output of the tubes steps down a small amount because of it. The B+ to the screens and all the preamp stages is up and down depending on current demand. Both are in more effect of the fluctuating B+ caused by the large value resistor then a simple low resistance choke. Does that change the sound of the amp? Maybe Does it change the feel of the amp? Maybe. Can an average decent player hear-feel it? Maybe. IMO, a choke is better overall but not critical and if you use a smaller value fixed resistor (270-500 ohms) to set the main and screens filter caps apart, you can install a seperate resistor to the screens from the second cap and get a very nice supply at a fraction of the cost of a choke. I doubt if chokeless amps are lacking in any bass if they are made correctly in the first place. You've been listening to cost driven uncool amps!! Bruce

3/13/2000 8:18 AM

Bruce

Re: Effect Of Chokes On Tone? /Probably too long!

Well, not taking into consideration the added benifit of less AC ripple from the inductance of a proper supply choke, what I've found to be at least equally important is the DC resistance of the choke and what pure DC resistance would be used (a resistor) in it's place.
When the DC resistance of the choke is low like under 100 ohms, then the voltage drop across it at idle and under load is less and ripple rejection is much better then a simple resistor.
Remember... I*R=E
More voltage is supplied to the screens and the preamp stages through a 90ohm choke then a 500 to 1000 ohm resistor (in the same place).
Current flow through either resistance will result in a voltage drop across that resistance, but, lower resistance creates lower voltage drop and higher current flow results in a larger voltage drop.
If the power tube's screens draw Xma of current under idle conditions and Xma x 2or3 when the amp is cranked up, that little 90ohms is not going to be dropping as much voltage as a 500 to 1000 ohm resistor.
Since the screen's voltage drops more with the larger screen resistor then a choke, the power output of the tubes steps down a small amount because of it.
The B+ to the screens and all the preamp stages is up and down depending on current demand.
Both are in more effect of the fluctuating B+ caused by the large value resistor then a simple low resistance choke.
Does that change the sound of the amp? Maybe
Does it change the feel of the amp? Maybe.
Can an average decent player hear-feel it? Maybe.

IMO, a choke is better overall but not critical and if you use a smaller value fixed resistor (270-500 ohms) to set the main and screens filter caps apart, you can install a seperate resistor to the screens from the second cap and get a very nice supply at a fraction of the cost of a choke.
I doubt if chokeless amps are lacking in any bass if they are made correctly in the first place.
You've been listening to cost driven uncool amps!!

Bruce

Replies:

Rebel420 IIRC, not only do some of the 'entr... -- 3/13/2000 2:44 PM
Ethan W Hi Bruce, thanks a lot for the info... -- 3/15/2000 6:19 AM